When a route of a path for transmitting a signal through a network is calculated, a calculation method as follows is performed. The network is divided into plural areas and the route of the path that passes through the areas is calculated for each area. In the specification, each of the plural areas obtained by dividing the network is referred to as a “domain”. FIG. 1 is a diagram illustrating an example of a network divided into plural domains. Reference symbol NT denotes a network. Reference symbol ND denotes a node device (also referred to as a “node”). The network NT includes plural node devices ND and links for connecting the node devices ND. The network NT is divided into plural domains. Reference symbols A1 to A3 denote domains formed by dividing the network NT.
Each domain is assigned with a route calculation apparatus that calculates the route in the domain. In the specification, the domain for which the route calculation apparatus performs route calculation may be referred to as a “target domain” of the route calculation apparatus. The route calculation apparatus assigned to each domain generates summarized data which is simplified data in regard to the network topology of the target domain and notifies the summarized data to the route calculation apparatuses assigned to other domains. Thus, the summarized data of a given domain is shared among the route calculation apparatuses of other domains except the given domain. The given domain obtains information on the network topology of each of the other domains except the given domain in the form of the summarized data.
In the calculation of the route of a path (referred to as a “target path”) to be set, a route calculation apparatus of a source domain including a source node device of the target path starts route calculation for the target domain and path setting by signaling. The route calculation apparatus executes calculation of a route within the target domain in accordance with detailed network topology data of the target domain, which is held in the route calculation apparatus. In the specification, a route of the target path within each domain may be referred to as an “intra-domain route”. When calculating the intra-domain route, the route calculation apparatus determines, in accordance with the summarized data, to which adjacent domain the intra-domain route is connected.
When a path of a certain domain has been set, a route calculation apparatus of an adjacent domain adjacent to the certain domain similarly calculates an intra-domain route connected to the set path and then sets the path therein. Each route calculation apparatus executes the similar process until reaching a destination domain including a destination node device, thereby setting the path passing through plural domains.
It is proposed that, in a hierarchical communication network divided into plural areas, when setting plural paths between a source node and a destination node via relay areas, a route calculation apparatus of a source area calculates relay routes of the paths in the source area, and each route calculation apparatus of a destination area and each relay area through which plural paths pass calculates relay routes of the paths in the destination area and each relay area in accordance with calculated relay routes of the paths.
Further, it is proposed that, in a large-scale network divided into plural areas, priority is placed among area boundary nodes in the same area, and cooperation is performed among the area boundary nodes, thereby setting a backup path without a shared link with a main path between the source-side end and the destination-side end.
Furthermore, a transmission device is proposed in a network divided into at least two areas including a first area and a second area. The transmission device is used as a boundary node between the two areas and sets a path between a source node in the first area and a destination node in the second area. The transmission device calculates, upon receiving from the first area a path request message based on a signaling protocol for setting a path, information relating to a route between the source node and the destination node in accordance with topology data of the first area and topology data of the second area. The transmission device transmits, to the source node, a message based on the signaling protocol, which includes the calculated information relating to the route.
Japanese Laid-open Patent Publication No. 2005-252368, Japanese Laid-open Patent Publication No. 2004-80211, and Japanese Laid-open Patent Publication No. 2008-85642 disclose related techniques.